In the process for producing a semiconductor device such as IC and LSI, microfabrication by lithography using a photoresist composition has been conventionally performed. Recently, with the increase in integration of an integrated circuit, formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using an electron beam, an X-ray or EUV light is also proceeding.
Such electron beam, X-ray or EUV light lithography is positioned as a next-generation or next-next-generation pattern formation technology, and a high-sensitivity and high-resolution resist composition is being demanded.
In particular, for shortening the wafer processing time, elevation of sensitivity is an important task, but when higher sensitivity is pursued, this causes deterioration in the pattern profile or the resolution represented by the limiting resolution line width, and development of a resist composition satisfying all of these characteristics at the same time is strongly demanded.
High sensitivity is in a trade-off relationship with high resolution and good pattern profile, and it is important how to satisfy all of these properties at the same time.
In order to solve such a problem, for example, in JP-A-8-101507 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-2000-29215, a positive resist composition using a resin having an acetal-type protective group is disclosed, and it is stated that according to this composition, the resolution, sensitivity and the like are improved.
In the positive image forming method, an isolated line or dot pattern can be successfully formed using this composition, but in the case of forming an isolated space or fine hole pattern, the pattern profile is liable to deteriorate.
In addition, a pattern forming method using an organic solvent-containing developer (organic developer) is also being developed recently (see, for example, JP-A-2010-217884). This method is supposed to enable stable formation of a high-definition fine pattern.
Furthermore, in recent years, the need for formation of a finer isolated space pattern or micronization of a hole pattern is abruptly increasing, as a result, in the case of forming a fine isolated space pattern having a space width of 100 nm or less, more performance improvement in terms of sensitivity, resolution and space width roughness is demanded. Similarly, in the case of forming a hole pattern having a fine hole diameter (for example, 50 nm or less), more performance improvement in terms of high resolution, good exposure latitude (EL) and local pattern dimension uniformity (Local-CDU) is demanded.